The present invention relates to testing systems for use in data processing networks.
Data processing networks in which a large number of users are joined by communication links extending over a large geographic area are becoming increasingly common. These networks consist of a collection of computers or computer terminals located at various sites. For the purposes of this discussion, the terms computer and computer terminal are defined to include any data processing unit. The computers communicate over communication paths which may include one or more telephone lines. Typically, a communication on one of these communication paths consists of a message sent from one network computer to another network computer. The message is formatted prior to transmission into a "packet" by adding certain, header and/or trailing information to the message. This additional information may include information defining the computer to which the information is to be sent as well as information which aids the receiving computer in interpreting the message and in verifying that the message has been properly transmitted over the network.
In addition to this packetization of the message, the message must be translated into one of a number of signaling formats before actually being sent over one of the network communication paths. The specific signaling format will, in general, depend on the specific type of communication path being used to communicate the message. For example, when a message is sent over a communication path which consists of a telephone line, each bit in the message is translated by a modem into a tone burst of a predetermined frequency which depends on whether the bit is a 1 or a 0. A similar modem at the other end of the telephone line receives these tone bursts and translates them back to digital signal levels representing the bits of the message.
When a data processing network fails to operate properly, it is often very difficult to ascertain the location and nature of the failed component. A failure may occur because of a malfunction in either the hardware or software associated with one of the computers, in one of the devices used to translate a packet from a digital format to a signaling format, or in one of the communication paths. Ascertaining the source of the malfunction is further complicated by the fact that the various pieces of equipment in the data processing network are typically supplied and serviced by different vendors with no single vendor having responsibility for the entire data processing network. As a result, the owner of the data processing network must first determine the source of the malfunction before the appropriate vendor will repair the malfunctioning component.
Testing systems for diagnosing data processing network malfunctions are known in the prior art. These systems are based on probes placed at various points in the data processing network for copying the signals present at specified points to a testing computer. These systems may also include one or more devices for generating test signals at specified points in the data processing network. The points at which signals are read or generated are usually just before or just after one of the network computers or signaling format devices. By examining the signals read at the various points in the data processing network and the response of the data processing network to the various signals generated by the test devices, the test computer determines which of the data processing network components has failed. The appropriate vendor may then be contacted to institute corrective measures.
Such prior art testing systems have three significant problems. First, a fault must be detected by one of the computers or computer operators in the data processing network. Until someone recognizes that the data processing network is not working properly, no diagnostic testing of the data processing network will be initiated. Intermittent equipment errors are very difficult to isolate. At most, the recipient of a message in the data processing network detects an error in the message. When such an error is detected, the sender of the message is notified of the error and the message is repeated. This message repeating service is often transparent to the computer operators using the data processing network. If the message is successfully received on the repeated attempt, no one is informed of the error. Such intermittent malfunctions often occur when a piece of equipment in the data processing network is just beginning to malfunction. Ideally one would like to detect such malfunctions as soon as possible and correct them before they cause the entire data processing network to be taken off line for unscheduled maintenance. In addition, if the malfunction remains at the intermittent level, it will reduce the throughput of the data processing network, since communication capacity used in repeating the erroneous messages can not be used to send new messages between the computers in the data processing network. This loss of capacity may go unnoticed for a significant period of time if a means for detecting such intermittent failures is not present in the data processing network.
Second, the prior art testing systems do not provide adequate security from eavesdropping by test personnel. The typical data processing network owner does not wish to maintain a service staff for diagnosing system failures. However, if the owner allows an outside vendor to install a testing system which can monitor the communications on the various communication paths in the data processing network, the confidentiality of the data being communicated within the data processing network may be breached. The prior art testing systems are designed to allow the test personnel full access to the data being sent and received over the various communication communication paths even though much of this data is irrelevant to detecting and isolating malfunctions in the data processing network.
Third, in general, prior art testing systems are designed to be used in testing only a very limited number of data processing networks. As a result, such testing systems include a significant amount of computer hardware which is idle when testing is not being carried out. More particularly, the probes for reading the signals at various locations in the data processing network and the devices for generating signals within the data processing network are, in general, coupled to a separate test computer system. This separate system must store data describing the data processing network to be tested and test programs tailored to that data processing network. Hence, a reasonably complex computer system must be employed. This computing capacity remains idle most of the time. Ideally, the testing system should allow this computer capacity to be used for other tasks. For example, it could be used to monitor and test several different data processing networks. In general, prior art testing systems are designed to be used in testing one data processing network.
Consequently, it is an object of the present invention to provide a diagnostic system and testing method for a data processing network which prevents the test personnel from acquiring sensitive information which is being sent and received on the various communication paths in the data processing network.
It is another object of the present invention to provide a means for detecting malfunctions prior to said malfunctions being recognized by the data processing network personnel.
It is yet another object of the present invention to provide a testing system in which the computer system used for performing the testing may be used to test a plurality of data processing networks.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.